i've been a superintendent for 30 some years at many different park service units across the united states. the only time i've ever had a break is when i was on maternity leave. i have retired from doing this one thing that i loved. now, i'm going to be able to have the time to explore something different. it's like another chapter. ♪ mile after mile, to and from ♪ now there are four for all to use ♪ ♪ tell the neighbors, friends, everyone the news ♪ ♪ and let's hum, hum, hum, hum ♪ ♪ let's hum ♪ a prius for everyone ♪ there's a bigger one, if you want more space ♪ ♪ a small one if the city's your place ♪ ♪ and even one you can plug in ♪ so hop on in and give one a spin ♪ ♪ and let's hum, hum, hum, hum ♪ ♪ let's hum ♪ a prius for everyone >>> back now at 8:20 with some big changes coming to twitter. the company's ceo will explain those in just a couple of minutes, but first jason kennedy gives us a look inside the company headquarters in san francisco. jason, good morning. >> reporter: hey there, matt, good morning. twitter is just six years old and